Boom travel limiting device for cranes



July 22, 1969 R. G ELY BOOM TRAVEL LIMITING DEVICE FOR CRANES 3 Sheets-Sheet 1 Filed Oct. 2. 1967 ROBERT 6. EL) INVENTOI? ATTORNEYS July 22, 1969 3. ELY 3,456,810

BOOM TRAVEL LIMITING DEVICE FOR CRANES Filed Oct. 2, 1967 5 Sheets-Sheet 2 w //?0 I 5638 47 4/8 X w I file Y \50\ AL/Xi! f x. X i

ROBERT 6. EL)

INVENTOP July 22, 1969 R. G. ELY 3,456,810

BOOM TRAVEL LIMITING DEVICE FOR CRANES Filed Oct. 2, 1967 5 Sheets-Sheet 5 FIG/0.

/05 ROBERT 6. EL r INVE N701? A TERA EV) United States Patent Office 3,456,810 Patented July 22, 1969 US. Cl. 212-39 Claims ABSTRACT OF THE DISCLOSURE A device for limiting the rotational travel of a boom arm on a crane providing at least one stop member adjustably mounted on a substantially circular support track and a cushioned bumper movable with the boom arm for engagement with the stop member. The device includes a control system movable with the boom arm for engagement with the StOp member ahead of the bumper to interrupt rotational power to the boom arm and to provide an audio signal to warn of the proximity of the bumper to the stop member and the boom arm to its predetermined limits of travel.

BACKGROUND OF THE INVENTION Mobile cranes having relatively long load lifting boom arms are frequently utilized adjacent to high-powered electrical conductor lines which, if contacted, usually result in extensive damage to the lines and injury to the crane operator and other workmen in the area. Such cranes are also frequently required to be parked closely adjacent to other obstructions and work objects such as buildings and the like that must be carefully avoided by the operator during manipulation of their boom arms toward and away from the adjacent structures. The relatively large mobile cranes conventionally include an elongated boom arm mounted on a power driven operators cab, the rotation and braking of which is controlled exclusively by the crane operator. Consequently, a high degree of care must be exercised by the operator in positioning the boom arm to avoid such hazards for his own safety and so as not to cause damage to the adjacent structures. Regulations have been imposed which seriously restrict the most etficient use of these cranes. Such regulations usually require that a crane of the type described cannot be parked in such proximity to a high tension wire or the like that if the boom falls, it cannot come within six feet of the wire. Accordingly, it is frequently necessary to employ a much larger crane than would ordinarily be required if the boom arm could be more accurately controlled and if it were possible to position the crane in closer proximity to the high tension wires or other work objects.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a boom travel limiting device for cranes and the like which permits the cranes to be positioned in optimum relation to a work object.

Another object is to provide such a boom travel limiting device which permits placement of the crane closely adjacent to a work object without danger of inadvertent contact of the boom with the work object.

Another object is to provide a boom travel limiting device of the character described which effectively limits the range of rotational movement of the boom and provides a positive stop for the boom arm at its extreme limits of travel in either direction.

Another object is to provide a boom travel limiting device having a pair of stop members which can be easily and conveniently mounted in a variety of positions to adjust the range of allowable boom movement between its extreme limits of travel and which can be completely removed to permit unrestricted boom rotation.

Another object is to provide a boom travel limiting device which includes a control system operatively connected to a powered drive mechanism for the boom arm which is effective automatically to neutralize the drive mechanism and to provide an audio signal to warn the operator when the boom approaches its extreme limits of travel.

Other objects and advantages of the present invention will subsequently become more clearly apparent upon reference to the following description in the specification and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a mobile crane having a boom travel limiting device of the present invention mounted thereon.

FIG. 2 is a somewhat enlarged side elevation of the boom travel limiting device and associated elements of the crane.

FIG. 3 is a further enlarged transverse vertical section through a stop member supporting track and showing a stop member on the track, in front elevation, as viewed in the direction of the arrows on line 33 of FIG. 2.

FIG. 4 is a side elevation of the boom arm stop member of FIG. 3.

FIG. 5 is a transverse vertical section through the frame of the crane showing the boom travel limiting device in front elevation.

FIG. 6 is a longitudinal horizontal section through the crane, taken on line 6-6 of FIG. 2, showing the boom travel limiting device in top plan view.

FIG. 7 is a somewhat enlarged top plan view of an impact cushioning and bumper assembly of the boom travel limiting device of the present invention.

FIG. 8 is a somewhat enlarged central longitudinal section through the cushioning and bumper assembly of FIG. 7.

FIG. 9 is a somewhat enlarged transverse vertical section through the cushioning and bumper assembly, taken generally along the line 9-9 of FIG. 8.

FIG. 10 is a diagrammatic view of an electric control system having an audio signal and a solenoid valve connected to the operators control lever for the crane.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to FIG. 1 of the drawings, a boom travel limiting device embodying the principles of the present invention is generally indicated by the reference numeral 10. The limiting device is shown in the preferred embodiment associated with a mobile crane 12 which is mounted upon a vehicle, such as the truck 14. The truck includes an elongated frame 15 which is supported for ground traversing movement by a plurality of sets of forward and rearward wheels '16 and 17, re'sp'ec' tively, with the frame beneath the crane being further supported adjacent to the rear wheels by removable legs 18.

The crane 12 includes an operators cab which is supported on the frame in the usual manner upon a circular bearing way or rail 22 providing a plurality of internally disposed rack teeth 23. A drive gear 25 is disposed in meshing relation with the rack teeth and is driven by its connection with a suitable power source, not shown, disposed within the cab. Rotation of the cab upon the hearing rail is effected by a control lever 26 within the cab which has connection to a suitable power train, not shown, between the drive gear 25 and the power source. An elongated boom arm 30 is pivotally mounted on the cab and is outwardly extended therefrom for vertical swinging movement relative to the cab on a pair of pivot shafts 32 extended through the lower end of the boom arm and a pair of brackets 33 on the cab.

A substantially circular stop mounting track is disposed on the frame 15 of the truck in concentric circumscribing relation to the bearing rail 22. The track is constructed of a pair of radially spaced concentric channels 42 which individually provide a plurality of ears 43 bolted to the frame 15 by cap screws 44. The track includes side portions 45 disposed in overhanging relation from the frame of the truck which are supported by shelf plates 47 outwardly extended from the frame. The side portions are secured to the shelf plates by suitable fastener bolts 48 extended through sets of ears 49 on the tracks. The track has spaced opposite ends 50 in order to provide access to the interior of the channels 42. The shelf plates are further supported by gussets 52 which, like the shelf plates, are rigidly secured to the frame, as by welding or the like.

As best shown in FIG. 6, a pair of boom arm stop blocks 55 are mounted on the track 40 in predetermined spaced relation individually adjacent to the opposite side portions 45 of the track. As best shown in FIGS. 3 and 4, each of the stop blocks is constructed of an L-shaped plate 56 having a lower substantially horizontal portion 57 and a substantially upright portion 58. Each stop block also includes opposite substantially triangular side plates 59 secured to the L-shaped plate, as by welding or' the like. An elongated block locking shoe 62 is slidably disposed within the track 40 between the channels 42 which is drawn in tightening relation against the stop block by a pair of clamping bolts 63 to secure the stop blocks in predetermined position on the track.

An impact cushioning bumper assembly is mounted on the cab 20 in outwardly extended relation therefrom in centered symmetrically disposed relation below the boom arm 30. As best shown in FIGS. 7, 8 and 9, the bumper assembly is mounted on an elongated hanger arm 72 having an inner end 73 secured to the under surface of the cab, as by welding or the like, and an opposite outer end 74 disposed in upwardly spaced relation above the track 40. The hanger arm is reinforced in such position by a pair of similarly secured angularly disposed gussets 75. Anelongated bumper mounting bracket has a central mounting portion 81 attached to the lower surface of the outer end of the hanger arm by a plurality of cap screws 82. As viewed in top plan in FIGS. 6 and 7, the bracket is constructed in the form of a shallow V so as substantially to coincide with the curvature of the track. The bracket includes opposite ends 84 disposed in depending right angular relation from the central mounting portion of the bracket with each end having a circular bore 85 therethrough. A pair of interior wall plates 87 are secured, as by welding or the like, midway between the opposite ends of the bracket and in spaced substantially parallel relation to their respectively associated ends so as to divide the bracket into opposite compartments 88. The compartments are partially enclosed by a plurality of substantially triangular side plates 89.

A divided bumper pad 90 of resilient yieldable material, such as rubber or the like, is bonded to the outer face of each' of the opposite ends 84 of the bracket on opposite sides of the bores 85. A pair of elongated spring mounting shafts 92 are individually mounted on the interior wall plates 87 in oppositely extended relation from each other into their respective compartments 88 of the bracket 80 and terminate in outer ends 93 somewhat short of their respective opposite ends 84 of the bracket. At each end of the bracket, an elongated cylindrical plunger 95 is eX- tended between the pads 90 and through the bore 85 is freely sliding relation. An elongated compression spring 96 provides an inner end 97 fitted about the mounting shaft 92 and an opposite outer end 98 receivable within the plunger 95. As best shown in FIG. 9, each of the plungers 95 includes a pair of diametrically opposed radially outwardly extended flanges 100 which engage the inner surface of their respective ends 84 of the bracket 80 to preclude complete separation of the plungers from the bracket.

A pair of normally open electrical limit switches are respectively associated with each of the plungers 95. As best shown in FIG. 8, the switches are mounted on the opposite ends 107 of a mounting strap 108 secured to the upper surface of the bumper assembly hanger arm 72 by the outermost pair of cap screws 82. It is noted that each end of the strap is offset downwardly to position the switches in a plane only slightly above a plane extended from the upper periphery of the plungers 95. Each of the switches 105 is of the one-way action type and includes a depending roller arm 110 which extends below its respective end 107 of the mounting strap for engagement with its respective stop block 55. An energizing button 112 is outwardly extended from the switch in the plane of the roller arm for engagement thereby during movement of the roller arm past the stop block.

It is noted that the switches 105 are circumferentially extended a predetermined distance from their associated plunger 95 so as to pass over the stop block prior to en gagement of the plunger with the stop block 55. As previously noted, mounting bracket 80 and the mounting strap 108 are oppositely angularly extended from the arm 72 in order substantially to follow the curvature of the stop block mounting track 40 and so the respective mating surfaces of the plungers 95 and the upright portion 58 of the stop blocks 55 abut each other in substantially fiat engagement.

As best shown in FIG. 10, each of the switches 105 is connected to an audio signal device such as the horn 114 and to a solenoid valve 115. The solenoid valve is connected through a lever 116 to the lower end of the operators control lever 26 in the cab 20 of the crane 12 so that upon actuation of the solenoid, the control lever is automatically returned to a neutral position.

OPERATION The operation of the described embodiment of the subject invention is believed to be clearly apparent and is briefly summarized at this point. Assuming that the mobile crane 12 and the truck 14 are parked with the legs 18 in ground engaging, crane supporting relation, as in FIG. 1, and adjacent to a building or other hazardous obstruction such as a high tension wire, the permissible distance that the boom arm 30 must be maintained from the hazard is determined for adjusting the stop blocks 55. In order to accomplish such adjustment, the clamping bolts 63 are loosened and the stop blocks and their associated locking shoes are slid along the track 40 to establish the predetermined limit of boom travel. It is noted, however, that if no obstruction is present adjacent to the crane, the stop blocks may be completely removed by sliding them outwardly of the track through the passage between its spaced ends 50 and stored in any convenient location on the crane. The stop blocks are quickly and conveniently installed by inserting their respective locking shoes into the passage between the channels 42 and sliding the shoes and blocks toward the side portions 45 of the track 40 to the desired locations and then tightening the clamping bolts 63.

Horizontal swinging movement of the boom arm 30 of the crane 12 is effected by manipulation of the control lever 26 to rotate the cab by connecting the drive gear to the power source. Such movement of the cab carries the switches 105 and the bumper assembly 70 along circumferentially above the track toward the appropriate stop block 55. Upon engagement of the stop block by the switch 105, the roller arm 110 is swung against the button 112 to close the switch and to energize the solenoid 115. As previously described, the control lever is returned to its neutral position to interrupt the power drive to the cab and to permit the boom arm and cab to coast the short distance between the switch and the plunger 95 of the bumper assembly 70.

Simultaneously with the interruption of power rotating the cab 20, the closing of the switch 105 energizes the horn 114 to provide an audio signal or warning to the operator that the extreme limit of travel of the boom arm has been nearly attained. Upon initial engagement of the plunger 95 with the upright portion 58 of the stop block 55, the spring 96 is compressed and the plunger initlally retracted into its respective compartment 88 of the bracket 80. As the momentum or rotational inertia of the cab 20 and boom arm 30 provides a further force tending to collapse the spring, the plunger is fully retracted so that its outer surface is substantially flush with the outer surface of the resilient bumper pads 90 which serves further to cushion the impact and to preclude further movement of the boom arm. Thus, the bumper assembly 70 absorbs inertial energy and slows rotation of the cab and boom arm. Upon manipulation of the control lever in the opposite direction, the rotation of the boom arm and cab is reversed whereupon the spring 96 is permitted to expand and to extend the plunger outwardly from the mounting bracket 80. Upon continued reverse movement of the cab, the roller arm 110 of the switch 105 is moved back over the stop block without affecting the control system.

In view of the foregoing, it is readily apparent that the structure of the boom travel limiting device of the present invention provides improved control of the boom arm on cranes which enables such cranes to be placed in optimum positions with respect to particular work objects and obstructions and precludes inadvertent or accidental contact of the boom arm with the work object or with other hazards adjacent thereto. The stop blocks can be quickly and conveniently adjusted to provide a wide range of boom arm travel and can be completely removed for unrestricted boom arm movement. Furthermore, the device of the present invention insures an automatic interruption of rotational power to the boom arm and a warning prior to impact of the bumper assembly with the stop blocks at the extreme limits of boom travel.

Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A boom travel limiting device for cranes having a frame, an operators cab rotatably supported on the frame and having an elongated outwardly extended boom arm for rotation therewith; comprising stop support means borne by the frame; stop means having a fixed part adjustably mounted on the support means; and bumper means mounted on the cab having an abutment part for engagement with said fixed part of the stop means to stop said rotation of the cab and boom arm, and resilient means associated with one of said parts for absorbing energy and slowing rotation of the cab and boom arm prior to stopping thereof.

2. The boom travel limiting device of claim 1 in which said cab and boom arm are power driven from a power source on the crane, and a control mechanism mounted on said cab adjacent to said bumper means for engagement with said stop means ahead of said bumper means and having controlling connection to said power source to interrupt the supply of rotating power to the crane prior to engagement of said bumper means with said stop means.

3. The boom travel limiting device of claim 1 in which said stop means includes a pair of spaced stop blocks, and said last-named means includes a pair of outwardly directed plungers inwardly movable incident to engagement with a stop block respectively, and spring means normally biasing the plungers outwardly and stressed by inward movement thereof for absorbing energy to overcome the inertia of rotation of the cab and boom arm.

4. A boom travel limiting device for cranes having an elongated frame providing opposite sides, an operators cab rotatably supported on the frame and having an elongated outwardly extended boom arm for rotation therewith through a predetermined arc of travel between said opposite sides of the frame, comprising a substantially circular stop support track on the frame; a pair of stop blocks slidably adjustably mounted on said track individually adjacent to said opposite sides of the frame; a pair of bumper members; and a bracket mounting said bumper members in oppositely extended relation on the cab for movement therewith above said track for engagement with their respectively adjacent stop blocks to limit rotation of the boom arm to said predetermined arc of travel; said bracket having opposite ends with substantially circular openings therethrough, said bumper members including elongated plungers individually extendible through said openings in the ends of the bracket, spring means normally biasing said plungers outwardly of their respective ends of the bracket and being retractable into said bracket between its ends incident to engagement of the bumper members with their respective stop blocks, and a pad of resilient material secured to each end of the bracket for engagement with its respective stop block upon full retraction of its associated plunger.

5. The boom travel limiting device of claim 4 in which said cab is rotated from a power source on the crane and includes an operators control lever movable between positions activating said cab and boom arm for rotation in either direction and a neutral position; and a control system mounted on said bracket having a pair of switch members disposed individually adjacent to said bumper members for engagement with said stop blocks ahead of their respective bumper members and providing controlling connection to said control lever to return it to its neutral position prior to engagement of said bumper members with said stop blocks, and an audio warning device energizable coincidentally with engagement of said switch members with said stop blocks.

6. A boom travel limiting device for cranes and the like having a supporting frame, a cab mounted for rotational movement on the frame and having an outwardly extended boom arm rotatable therewith, cooperating bumper means and stop means, one thereof being mounted on the frame and the other on the cab, each of said means including an abutting part, said parts being engageable during movement of the cab for positively stopping such movement, and movable energy absorbing means associated with one of the abutting parts operable to overcome the rotational inertia of the cab and its boom arm for slowing movement thereof prior to stopping.

7. The device of claim 6 in which the energy absorbing means includes spring pressed means engageable with the other part for stressing the spring pressed means prior to engagement of the last-named part with said one part.

8. The device of claim 6 in which the energy absorbing means includes a plunger slidably mounted on said one part, and resilient means urging the plunger outwardly toward said other part, said resilient means being operable to absorb energy upon inward movement of the plunger.

9. The device of claim 6 in which the stop means includes a pair of spaced abutment members adjustably secured to the supporting frame, and said bumper means includes a pair of oppositely directed biased plungers mounted on the cab intermediate the abutment members.

10. The device of claim 9 in which the plungers are slidably mounted in the bumper means, and compression springs associated with the piungers biasing each away from the other.

References Cited UNITED STATES PATENTS 2,529,193 11/1950 Rueter 212-39 10 8 3,170,411 2/1965 Howard 104-44 3,285,430 11/1966 Whitmire 212-39 3,369,671 2/ 1968 Yasukouchi 21259 EVON C. BLUNK, Primary Examiner HARVEY C. HORNSBY, Assistant Examiner US. Cl. X.R. 

